1. Field of the Invention
The present invention pertains to medical equipment, and more particularly, to a therapeutic ultrasound system for ablating obstructions within tubular anatomical structures such as blood vessels. The ultrasound system includes a protective feature that minimizes the introduction of debris into the patient's vasculature if the ultrasound transmission member were to break, fracture or become dislodged during a medical procedure. The ultrasound system also includes a distal tip configuration that increases energy intensity and reduces perforations.
2. Description of the Prior Art
A number of ultrasound systems and devices have heretofore been proposed for use in ablating or removing obstructive material from blood vessels. Ultrasound catheters have been utilized to ablate various types of obstructions from blood vessels of humans and animals. Successful applications of ultrasound energy to smaller blood vessels, such as the coronary arteries, requires the use of relatively small diameter ultrasound catheters which are sufficiently small and flexible to undergo transluminal advancement through the tortuous vasculature of the aortic arch and coronary tree. However, because of its small diameter, the ultrasound transmission member which extends through such catheters is particularly susceptible to losses in the transmitted ultrasound energy, and breakage. Reducing the size of the ultrasound transmission member, particularly the distal tip, will increase energy intensity. However, it will also make the distal tip of the ultrasound transmission member more prone to perforations due to inherited stiffness of the transmission member and a smaller tip size.
Breakage of ultrasound transmission members often occurs near the proximal end thereof, generally at the coupling between the ultrasound catheter coupling and the ultrasound transducer. This is believed to be because energy concentrations and stresses are highest at these points. Thus, any external forces applied to the ultrasound transmission member in this region may result in stresses exceeding the elastic limit of the ultrasound transmission member.
Breakage of ultrasound transmission members can also occur near the distal end thereof, generally at the area of the smallest cross-section. To minimize breakage of the ultrasound transmission wire at the distal end, a smaller distal tip with less mass or a tip made of polymer or a lower density metal may be utilized to further reduce stress at the distal in on the transmission wire. It is important that any debris resulting from the breakage of the ultrasound transmission member not be allowed to be introduced into a patient's vasculature during a medical procedure.
Thus, there still exists a need to further improve efficacy of the ultrasound systems and protect against breakage of the ultrasound transmission member during a medical procedure.